A foot-rule found at Warrington gave a length of 11·54 in. The normal Roman foot is said to be 11·6496 in. (also 0·2957 m.). This agrees closely with the Greek foot and the Chaldean. (What is the history of the English foot?) The length of the Roman foot, a little over 11½ of our inches, is worth remembering, for measurements would have been set out by this standard. For example, we may examine the ordinary building “tile” used in Londinium. In the Lombard Street excavations of 1785 many Roman bricks were found which are said to have measured about 18 in. by 12 in. I have found this measurement many times repeated, and also three more precise estimates. Dr. Woodward said that bricks from London Wall were 17-4/10 in. by 11-6/10 in., and he observed that this would be 1½ by 1 Roman foot. Mr. Loftus Brock gave the size of one found in London Wall as 17 in. by 11⅝ in. Dr. P. Norman gave the size of another tile as about 17½ in. by nearly 12 in. At the Guildhall are several flue and roof tiles about 17½ in. long, and a large tile 23¼ in. long. We shall see when we come to examine buildings that the dimensions in many cases are likely to have been round numbers of Roman feet. _Masonry._—Walling had three main origins in mud, timber and stone. Walling stones were at first, and for long, packed together without mortar. Mud and stone were then combined; later, lime mortar took the place of mud, being a sort of mud which will set harder. In concrete, again, the mortar became the principal element. Stone walling was at first formed of irregular lumps. When hewn blocks came to be used a practice arose of linking them with wood or metal cramps. There are also three main types of wall construction—aggregation of mud, framing of timber, and association of blocks of stone. A later development of mud walling was to break up the material, by analogy with hewn stone, into regular lumps separately dried before they were used; thus crude bricks, the commonest building material in antiquity, were formed. Roofing tiles were developed from pottery, and such tiles came to be used for covering the tops of crude brick walls. Then, later, whole walls were formed of baked material, and thus the tile or brick wall was obtained. An alternative method of using mud was to daub it over timber or wattle (basket work) of sticks; and this seems to have been a common procedure in Celtic Britain. Interesting varieties of concrete walling were developed by Roman builders. One of these was the use of little stones for the faces of a wall, tailing back into the concrete mass and forming a hard skin or mail on the surfaces, very like modern paving. Triangular tiles with their points toothed into the concrete mass were also used. Then tile courses were set in stone and concrete walls at every few feet of height.